Stretch forming apparatus

ABSTRACT

A stretch forming apparatus comprises a pair of jaws for pinching both ends of a work, a die placed between the pair of jaws so as to be in contact with the work, a plurality of control axis for change in positions and postures of the jaws and the die, a rotation center line setting unit for making an operator set rotation center lines for the jaws that are for partial stretch of the work by rotation of the jaws, an operation input unit for rotating the jaws by manual operation about the rotation center lines, and a control unit for synchronously controlling the plurality of control axis so that the jaws rotate in accordance with the manual operation by the operator on the operation input unit about the rotation center lines.

TECHNICAL FIELD

The invention relates to a stretch forming apparatus for performing stretch forming for a work.

BACKGROUND ART

Conventionally, stretch forming has been used by which a work is stretch-formed into a desired shape. As described in Patent Literature 1, for instance, the stretch forming is performed with use of a stretch forming apparatus including a pair of jaws for pinching end edge side parts of the work having a pair of side edges and a pair of end edges, a die that is placed between the pair of jaws so as to be in contact with the work, and a plurality of control axis for change in positions and postures of the jaws and the die. An operator manually operates the plurality of control axis to change the positions and postures of the jaws and the die so that the work is wound around the die and is stretch-formed into the desired shape.

CITATION LIST Patent Literature

-   PTL1: JP 2009-523613 A

SUMMARY OF INVENTION Technical Problem

In the stretch forming of a work, the work may be desired to be partially stretched. For instance, creases caused partially on the work may be desired to be stretched.

It is difficult, however, to partially stretch the work in the stretch forming apparatus disclosed in Patent Literature 1 described above. For instance, it is difficult for the operator to manually operate the plurality of control axis so as to stretch one of the pair of side edges of the work, while suppressing deformation of the other side edge thereof, in order to stretch creases caused on the one side edge of the work.

It is also difficult to manually operate the plurality of control axis so that one part of the work more intimate contacts with the die in comparison with the remaining part thereof and so that the one part thereof is greatly stretched to be deformed, for example.

In the stretch forming apparatus disclosed in Patent Literature 1, in particular, it is difficult to manually operate the plurality of control axis so as to partially stretch the work because translation of the jaws is restricted to two directions by a configuration of the axis of the apparatus.

Therefore, it is an object of the invention to simplify manual operation that an operator performs for partially stretching a work in a stretch forming apparatus.

Solution to Problem

In order to achieve the object, according to a first aspect of the invention, there is provided a stretch forming apparatus comprising:

a pair of jaws for pinching end edge side parts of a work having a pair of side edges and a pair of end edges;

a die placed between the pair of jaws so as to be in contact with the work;

a plurality of control axis for change in positions and postures of the jaws and the die;

a rotation center line setting unit for making an operator set rotation center lines for the jaws that are for partial stretch of the work by rotation of the jaws,

an operation input unit for rotating the jaws by manual operation about the rotation center lines set by the operator through the rotation center line setting unit, and

a control unit for synchronously controlling the plurality of control axis so that the jaws rotate, in accordance with the manual operation by the operator on the operation input unit, about the rotation center lines set by the operator through the rotation center line setting unit.

According to a second aspect of the invention, there is provided the stretch forming apparatus according to the first aspect of the invention, wherein the rotation center line setting unit is configured so as to set the rotation center lines by positions and postures in jaw coordinate systems predefined for the jaws, and wherein

the control unit defines the rotation center lines for the jaws that have been defined by the positions and postures in the jaw coordinate systems, by positions and postures in a die coordinate system predefined for the die and controls the control axis for the die and the control axis for the jaws so that the jaws rotate about the rotation center lines defined by the positions and postures in the die coordinate system.

According to a third aspect of the invention, there is provided the stretch forming apparatus according to the first aspect of the invention, wherein the rotation center line setting unit sets the rotation center lines so that the rotation center lines pass through crossing points of a side edge of the work and boundaries between parts of the work pinched by the jaws and the remaining parts thereof.

According to a fourth aspect of the invention, there is provided the stretch forming apparatus according to the third aspect of the invention, wherein the rotation center line setting unit sets the rotation center lines that extend in a direction orthogonal to surfaces of the parts of the work pinched by the jaws.

According to a fifth aspect of the invention, there is provided the stretch forming apparatus according to the third aspect of the invention, wherein the rotation center line setting unit sets the rotation center lines along an extending direction of side edges in the parts of the work pinched by the jaws.

According to a sixth aspect of the invention, there is provided the stretch forming apparatus according to the first aspect of the invention, wherein, on condition that there are a plurality of combinations of the control axis that allow the jaws to be rotated about the rotation center lines set by the operator, the control unit selects a combination including the largest number of the control axis of which quantities of operation for rotation of the jaws are smaller than a specified value, and rotates the jaws by controlling the control axis included in the selected combination.

Advantageous Effects of Invention

according to the invention, the manual operation for a partial stretch of a work is simplified because the operator has only to conceive the rotation center lines for the jaws that are for the partial stretch of the work by the rotation of the jaws, that is, because the operator does not have to conceive the manual operation of each of the plurality of the control axis.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a model diagram showing a configuration of control axis of a stretch forming apparatus in accordance with an embodiment of the invention;

FIG. 2 is a diagram for illustrating stretch forming that is performed by the stretch forming apparatus in accordance with the embodiment;

FIG. 3 is a diagram for illustrating rotation of jaws that is for partial stretch of a work;

FIG. 4 are diagrams for illustrating an example in which the work is partially stretched by movement of a plurality of control axis;

FIG. 5 are diagrams for illustrating another example in which the work is partially stretched by movement of the plurality of control axis; and

FIG. 6 are diagrams for illustrating still another example in which the work is partially stretched in the same manner as in the example shown in FIG. 5 by movement of the control axis other than those of the example shown in FIG. 5.

DESCRIPTION OF EMBODIMENTS

FIG. 1 is a diagram schematically showing a configuration of a stretch forming apparatus in accordance with an embodiment of the invention.

As shown in FIG. 1, the stretch forming apparatus 10 has a pair of jaws J_(L), J_(R) for pinching end edge side parts of a plate-like work W having a pair of end edges and a pair of side edges and a die D that is placed between the pair of jaws J_(L), J_(R) so as to be in contact with the work W.

In the stretch forming apparatus 10 is defined a system coordinate system ΣS composed of an X axis, a Y axis and a Z axis that are orthogonal to one another. The X axis direction and the Y axis direction are horizontal directions and the Z axis direction is a vertical direction.

For the die D, to be more precise, for a die table T onto which the die D is repiaceably fixed, a die table coordinate system ΣD is defined that is composed of an X_(D) axis, a Y_(D) axis and a Z_(D) axis which are orthogonal to one another. An origin of the die table coordinate system ΣD is positioned at a center of the table T and is positioned on the Z axis of the system coordinate system ΣS.

Jaw coordinate systems ΣJ_(L), ΣJ_(R) that are rectangular coordinate systems are defined for the jaws J_(L), J_(R), respectively. Origins of the jaw coordinate systems ΣJ_(L), ΣJ_(R) are positioned on reference points P_(JL) P_(JR) of the jaws J_(L), J_(R) that are positioned at holding centers of the jaws J_(L), J_(R) for the work W. When the jaws J_(L), J_(R) appropriately pinch the work W, the reference points P_(JL), P_(JR) are positioned at centers of the parts of the work W pinched by the jaws J_(L), J_(R), and surfaces of the parts of the work W pinched by the jaws J_(L), J_(R) are made orthogonal to Z_(JL) and Z_(JR) axes.

The stretch forming apparatus 10 further has a die table up-and-down axis J_(D1) for movement of the die D (die table T) in the vertical direction (Z axis direction) relative to a base B of the stretch forming apparatus 10 and a die table tilt axis J_(D2) for rotation of the die D about a rotation center line C_(D1) extending in parallel with the X axis, as die control axis for change in the position and posture of the die.

The stretch forming apparatus 10 further has a carriage axis J_(L1) for strokes of the jaw J_(L) in parallel with the X axis, an angulation axis J_(L2) for rotation of the jaw J_(L) about a rotation center line C_(L1) extending in parallel with the Z axis, a slider axis J_(L3) for strokes of the jaw J_(L) in a horizontal direction (in parallel with an X-Y plane), a swing axis J_(L4) for rotation of the jaw J_(L) about a rotation center line C_(L2) extending in parallel with the direction of the strokes of the slider axis J_(L3), a tension axis J_(L5) for strokes of the jaw J_(L) in a direction of a straight line orthogonal to the rotation center line C_(L2) of the swing axis J_(L4), and a rotation axis J_(L6) for rotation of the jaw J_(L) about a rotation center line C_(L3) extending in the direction of the strokes of the tension axis J_(L5), in order of placement from the base B of the stretch forming apparatus 10 toward the jaw J_(L), as control axis for the jaw J_(L) for change in the position and posture of the jaw J_(L). The direction of the strokes of the tension axis J_(L5) coincides with an X_(JL) axis direction of the jaw coordinate system ΣJ_(L).

Similarly, the stretch forming apparatus 10 further has a carriage axis J_(R1) for strokes of the jaw J_(R) in parallel with the X axis, an angulation axis J_(R2) for rotation of the jaw J_(R) about a rotation center line C_(R1) extending in parallel with the Z axis, a slider axis J_(R3) for strokes of the jaw J_(R) in a horizontal direction (in parallel with the X-Y plane), a swing axis J_(R4) for rotation of the jaw J_(R) about a rotation center line C_(R2) extending in parallel with the direction of the strokes of the slider axis J_(R3), a tension axis J_(R5) for strokes of the jaw J_(R) in a direction of a straight line orthogonal to the rotation center line C_(R2) of the swing axis J_(R4), and a rotation axis J_(R6) for rotation of the jaw J_(R) about a rotation center line C_(R3) extending in the direction of the strokes of the tension axis J_(R5), in order of placement from the base B of the stretch forming apparatus 10 toward the jaw J_(R), as control axis for the jaw J_(R) for change in the position and posture of the jaw J_(R). The direction of the strokes of the tension axis J_(R5) coincides with an X_(JR) axis direction of the jaw coordinate system ΣJ_(R).

Such a plurality of control axis provide the jaws J_(L), J_(R) with six degrees of freedom in the die table coordinate system ΣD. That is, the jaws J_(L), J_(R) can be translated in the X_(D) axis direction, the Y_(D) axis direction, and the Z_(D) axis direction of the die table coordinate system ΣD and can be rotated about the X_(D) axis, the Y_(D) axis, and the Z_(D) axis.

In addition, the stretch forming apparatus 10 has a control unit (not shown) for controlling the fourteen control axis J_(D1), J_(D2), J_(L1) through J_(L6), and J_(R1) through J_(R6). For each of the control axis J_(D1), J_(D2), J_(L1) through J_(L6), and J_(R1) through J_(R6), specifically, the stretch forming apparatus 10 has a driving cylinder (not shown) for driving the control axis. The control unit controls the driving cylinders.

The driving cylinders for driving the control axis J_(D1), J_(D2), J_(L1) through J_(L6), and J_(R1) through J_(R6) are hydropneumatic cylinders (e.g., hydraulic cylinders) in each of which hydraulic pressures are supplied to a rod side cylinder chamber and a head side cylinder chamber that adjoin each other across a piston. The control unit controls hydraulic system components such as electromagnetic valves and hydraulic pumps (not shown), thereby regulates the hydraulic pressures that are supplied to the rod side cylinder chamber and the head side cylinder chamber, and thereby controls the driving cylinders for the control axis J_(D1), J_(D2), J_(L1) through J_(L6), and J_(R1) through J_(R6).

The control unit of the stretch forming apparatus 10 is configured so as to perform position control for controlling positions of the pistons relative to the driving cylinders and pressure control for controlling cylinder output. The stretch forming apparatus 10 is configured so that an operator can select whether the driving cylinder is subjected to the position control or the pressure control for each of the control axis J_(D1), J_(D2), J_(L1) through J_(L6), and J_(R1) through J_(R6).

The rotation axis such as the die table tilt axis J_(D2), the angulation axis J_(L2), J_(R2), the swing axis J_(L4), J_(R4), and the rotation axis J_(L6), J_(R6) make the jaws J_(L), J_(R) rotate within specified angle ranges through crank mechanisms by advance and retreat of rods of the driving cylinders. Angle positions of the jaws about the rotation center lines of the rotation axis are controlled by the position control by the control unit for the driving cylinders. Otherwise, torques of the rotation axis are controlled by the pressure control for the driving cylinders.

The translation axis such as the die table up-and-down axis J_(D1), the carriage axis J_(L1), J_(R1), the slider axis J_(L3), J_(R3), and the tension axis J_(L5), J_(R5) cause the jaws J_(L), J_(R) to make strokes within specified ranges by advance and retreat of the driving cylinders. Positions of the jaws within the ranges of the strokes of the translation axis are controlled by the position control by the control unit for the driving cylinders. Otherwise, thrusts of the translation axis are controlled by the pressure control for the driving cylinders.

Herein, the control axis (driving cylinders) are subjected to the position control unless there is specification of “pressure control”.

In addition, the stretch forming apparatus 10 is configured so that an operator can manually operate the control axis J_(D1), J_(D2), J_(L1) through J_(L6), and J_(R1) through J_(R6). For each of the control axis J_(D1), J_(D2), J_(L1) through J_(L6), and J_(R1) through J_(R6), specifically, the stretch forming apparatus 10 has an operation input unit (not shown) for the manual operation by the operator.

For instance, the operation input unit is composed of buttons. While the operator remains pressing a button, the corresponding control axis is controlled by the control unit so as to continue operating at a predetermined fixed velocity. When the operator presses a button one time, for instance, the corresponding control axis is controlled by the control unit so as to operate by a predetermined quantity of operation.

While the operator remains pressing a “die move-up” button on the operation input unit that is for the manual operation of the die table up-and-down axis J_(D1) and that is composed of the “die move-up” button and a “die move-down” button, for example, the control unit controls the die table up-and-down axis J_(D1) so that the die D continues moving up at a predetermined velocity. When the “die move-up” button is pressed one time, the die D moves up by a predetermined quantity of movement.

The operator winds the work around the die by the manual operation of the plurality of the control axis J_(D1), J_(D2), J_(L1) through J_(L6), and J_(R1) through J_(R6) by way of the operation input units.

For winding the work W around the die D while suppressing extensional deformation of the work W, for instance, the operator makes the jaws J_(L), J_(R) approach the die D by the manual operation of the carriage axis J_(L1), J_(R1) while moving up the die D being in contact with the work W by the manual operation of the die table up-and-down axis J_(D1) so as to prevent the work W from being elongated, as shown in FIG. 2. In addition to the die table up-and-down axis J_(D1) and the carriage axis J_(L1), J_(R1), as shown in FIG. 2, the operator manually operates the swing axis J_(L4), J_(R4) so that directions in which the work W extends from the jaws J_(L), J_(R) toward the die D coincide with the directions of the strokes of the tension axis J_(L5), J_(R5) and manually operates the tension axis J_(L5), J_(R5).

Furthermore, the stretch forming apparatus 10 is configured so that the operator can easily perform partial stretch of the work W.

Herein, “partially stretching the work” refers to more greatly stretching a part of the work the operator demands than other parts thereof.

The operator may desire to partially stretch the work W while performing the stretch forming by the manual operation of the plurality of the control axis J_(D1), J_(D2), J_(L1) through J_(L6), and J_(R1) through J_(R6) as described above.

As shown in FIG. 3, for instance, the operator may desire to suppress deformation of one side edge W_(F) (front side) of the work W while stretching creases caused on the other side edge W_(B) (back side) thereof. The side edge W_(B) side of the work W may be desired to be more greatly stretched than the side edge W_(F) side thereof with the side edge W_(B) side of the work W more strongly pressed against the die D than The side edge W_(F) side, for instance. In such a case, it is necessary but difficult for the operator to think how to manually operate the plurality of the control axis J_(D1), J_(D2) J_(L1) through J_(L6), and J_(R1) through J_(R6).

In order to cope with that, the stretch forming apparatus 10 is configured so as to partially stretch the work W by rotating the jaws J_(L), J_(R) about the rotation center lines set for the jaws J_(L), J_(R) and set in appropriate relative positions with respect to the die D. The apparatus is configured so that the appropriate rotation center lines for the jaws J_(L), J_(R) are set by the operator.

For that purpose, the stretch forming apparatus 10 has a rotation center line setting unit (not shown) as means for the operator setting the rotation center lines for the jaws J_(L), J_(R) and the operation input units (not shown, the units will be referred to as “operation input units for partial stretch” below) as means for rotating the jaws J_(L), J_(R) by the manual operation about the set rotation center lines.

Specifically, it is apparently easier to conceive the rotation center lines for the jaws J_(L), J_(R) that are required for stretching the side edge W₆ of the work W, because it is intuitive, than to conceive the manual operation of the plurality of the control axis J_(D1), J_(D2), J_(L1) through J_(L6), and J_(R1) through J_(R6) that are required for stretching the side edge W_(B) of the work W, as shown in FIG. 3, for instance.

For example, it is easy for the operator to conceive a rotation center line A1 that passes through a crossing point C1 of the side edge W_(F) and a boundary between a part (shaded part) of the work W pinched by the jaw J_(L) and the remaining part and that extends in parallel with the Z_(JL) axis direction of the jaw coordinate system τJ_(L), and a rotation center line A2 that passes through a crossing point C2 of the side edge W_(F) and a boundary between a part (shaded part) of the work W pinched by the jaw J_(R) and the remaining part and that extends in parallel with the Z_(JR) axis direction of the jaw coordinate system ΣJ_(R).

Besides, it is intuitive and apparently easier to conceive the rotation center lines for the jaws J_(L), J_(R) that are required for stretching the side edge W_(B) side of the work W by strongly pressing the side against the die D than to conceive the manual operation of the plurality of the control axis J_(D1), J_(D2), J_(L1) through J_(L6), and J_(R1) through J_(R6) that are required for stretching the side edge W_(B) side of the work W by strongly pressing the side against the die D. For instance, it is easy to conceive a rotation center line A3 that passes through the point C1 and that extends in parallel with the X_(JL) axis direction of the jaw coordinate system ΣJ_(L), and a rotation center line A4 that passes through the point C2 and that extends in parallel with the X_(jR) axis direction of the jaw coordinate system ΣJ_(R).

For facilitation of understanding, the work W is shown in a flat state in FIG. 3. It is obvious and intuitively comprehensible to the operator that the side edge W_(B) of the work W can be stretched or can be strongly pressed against the die D by setting of the rotation center lines A1, A2 or A3, A4 and the rotation of the jaws J_(L), J_(R) about the set rotation center lines even though the work W is wound around the die D (i.e., even in midst of the stretch forming).

The rotation center line setting unit of the stretch forming apparatus 10 is an input unit such as numeric keypad and keyboard through which numerals can be inputted and is configured so that the operator sets and inputs the rotation center lines for the jaws J_(L), J_(R) for the partial stretch of the work W with use of positions and postures in the Jaw coordinate systems ΣJ_(L), ΣJ_(R).

For setting the rotation center lines for the jaws J_(L), J_(R) for the partial stretch of the work W, specifically, the operator concretely defines the positions (coordinates) and postures (directions) of the rotation center lines. It is easier to define the rotation center lines for the jaws J_(L), J_(R) by the positions (coordinates) and postures (directions) in the jaw coordinate systems ΣJ_(L), ΣJ_(R) than to define those in other coordinate systems such as the system coordinate system ΣS.

A position (coordinate) of the point C1, through which the rotation center lines A1, A3 and the like pass, of the work W in the jaw coordinate system ΣJ_(L) can easily be calculated from a shape of the jaw J_(L), a size of the work W and the like, as shown in FIG. 3, for instance. The directions in which the rotation center lines A1, A3 and the like extend can be defined by two points in the jaw coordinate system ΣJ_(L).

Once the operator sets the rotation center lines for the jaws J_(L), J_(R) and thereafter performs the manual operation for the operation input units for partial stretch, the control unit of the stretch forming apparatus 10 rotates the jaws J_(L), J_(R) about the rotation center lines, set by the operator, in accordance with the manual operation by the operator.

The operation input units for partial stretch for causing manual rotation of the jaws J_(L), J_(R) are each composed of a “+” button and a “−” button, for instance. While the operator remains pressing the “+” button for the jaw J_(L), for instance, the control unit of the stretch forming apparatus 10 controls the plurality of control axis J_(D1), J_(D2), J_(L1) through J_(L6), and J_(R1) through J_(R6) so as to continue rotating the jaw J_(L) about the rotation center line set by the operator at a predetermined rotation velocity. When the operator presses the “+” button only one time, the control unit rotates the jaw J_(L) by a predetermined quantity of rotation.

Specifically, the control unit of the stretch forming apparatus 10 initially redefines the rotation center lines for the jaws J_(L), J_(R), defined by the positions and postures in the jaw coordinate systems ΣJ_(L), ΣJ_(R) set by the operator, by positions and postures in the die table coordinate system ΣD with coordinate transformation. Thus the rotation center lines for the jaws J_(L), J_(R) are set in appropriate relative positions with respect to the die D.

The control unit of the stretch forming apparatus 10 is configured so as to subsequently calculate operation velocities (quantities of operation per unit time) of the plurality of the control axis J_(D1), J_(D2), J_(L1) through J_(L6), and J_(R1) through J_(R6) on basis of the rotation center lines for the jaws J_(L), J_(R) that are defined by the positions and postures in the die table coordinate system ΣD and on basis of the rotation velocity (quantities of rotation per unit time) for the jaws J_(L), J_(R) that correspond to the manual operation by the operator.

For description, as shown in FIG. 4(A), an example is adduced in which the rotation center line A1 is set in an appropriate relative position with respect to the die D so as to pass through the crossing point C1 of the side edge W_(F) and the boundary of the part of the work W pinched by the jaw J_(L) and so as to extend in parallel with the Z_(D) axis of the die table coordinate system ΣD. For facilitation of understanding, FIG. 4(A) shows the example in which the work W is horizontally extended into a flat state, that is, the example in which the Z_(JL) axis of the jaw coordinate system ΣJ_(L) is parallel to the Z_(D) axis of the die table coordinate system ΣD.

The quantities of operation of the plurality of the control axis J_(D1), J_(D2), J_(L1) through J_(L6), and J_(R1) through J_(R6) that are for rotating the jaw J_(L) by a quantity of rotation Δθ1 about the rotation center line A1 set in the appropriate relative position with respect to the die D are calculated on basis of a configuration (e.g., distances between the control axis) of the axis of the stretch forming apparatus 10 with use of an inverse kinematics algorithm. As shown in FIG. 4(B), a quantity of movement ΔX of the carriage axis J_(L1), a quantity of rotation Δα of the angulation axis J_(L2), and a quantity of movement ΔS1 of the slider axis J_(L3) are calculated as the quantities of operation of the control axis that are required for the rotation of the jaw J_(L) by the quantity of rotation Δθ1 about the rotation center line A1. The quantities of operation of the remaining control axis are made zero.

As shown in FIG. 5(A), another example is adduced in which the rotation center line A3 is set in an appropriate relative position with respect to the die D so as to pass through the point C1 and so as to extend in parallel with the X_(D) axis of the die table coordinate system ΣD. For facilitation of understanding, FIG. 5(A) shows the example in which the work W is horizontally extended into a flat state, that is, the example in which the Z_(JL) axis of the jaw coordinate system ΣJ_(L) is parallel to the Z_(D) axis of the die table coordinate system ΣD.

As shown in FIG. 5(B), a quantity of movement ΔZ1 of the die table up-and-down axis J_(D1), a quantity of movement ΔS2 of the slider axis J_(L3), and a quantity of rotation Δβ of the rotation axis J_(L6) are calculated as the quantities of operation of the control axis that are required for rotating the jaw J_(L) by a quantity of rotation Δθ2 about the rotation center line A3 set in the appropriate relative position with respect to the die D. The quantities of operation of the remaining control axis are made zero.

Upon calculating the operation velocities (quantities of operation per unit time) of the plurality of the control axis J_(D1), J_(D2), J_(L1) through J_(L6), and J_(R1) through J_(R6), the control unit of the stretch forming apparatus 10 operates (synchronously controls) the control axis J_(D1), J_(D2), J_(L1) through J_(L6), and J_(R1) through J_(R6) at the calculated operation velocities.

In the example shown in FIG. 5, for instance, the control unit of the stretch forming apparatus 10 moves up the die D by the quantity of movement ΔZ1 by the die table up-and-down axis J_(D1), translates the jaw J_(L) (J_(R)) in the Y axis direction by the quantity of movement ΔS2 by the slider axis J_(L3) (J_(R3)), and rotates the jaw J_(L) (J_(R)) by the quantity of rotation Δβ by the rotation axis J_(L6) (J_(R6)). Thus the jaw J_(L) (J_(R)) is rotated by Δθ2 about the rotation center line A3 (A4) set by the operator and the side edge W_(B) side of the work W is stretched by being brought into contact with and pressed against the die D.

According to the embodiment, the manual operation for the partial stretch of the work W can be facilitated because the operator has only to conceive the rotation center lines for the jaws J_(L), J_(R) that are for the partial stretch of the work W by the rotation of the jaws J_(L), J_(R), that is, because the operator does not have to conceive the manual operation of each of the plurality of the control axis J_(D1), J_(D2), J_(L1) through J_(L6), and J_(R1) through J_(R6).

Though having been described above with adduction of the embodiment, the invention is not limited thereto.

In the embodiment described above, for instance, the rotation center lines for the jaws J_(L), J_(R) that are for the partial stretch of the work W by the rotation of the jaws J_(L), J_(R) are defined as the positions and postures in the jaw coordinate systems ΣJ_(L), J_(R) by the operator. The invention, however, is not limited thereto. The rotation center lines for the jaws J_(L), J_(R) may be defined as positions and postures in coordinate systems other than the jaw coordinate systems ΣJ_(L), J_(R), e.g., the die table coordinate system ID, the system coordinate system IS or the like.

On condition that the operator selects either of the pair of side edges W_(F), W_(B) of the work W the operator desires to stretch, as shown in FIG. 3, for instance, the rotation center line setting unit of the stretch forming apparatus 10 may set the rotation center lines on the other side edge of the work W the operator does not select. When the operator selects the side edge W_(B) of the work W, in FIG. 3 as an example, the rotation center line setting unit sets the rotation center lines A1, A2 that pass through the crossing points C1, C2 of the side edge W_(F) and the boundary between the parts of the work W pinched by the jaws J_(L), J_(R) and the remaining parts.

Depending upon the configuration of the axis of the stretch forming apparatus, there may be a plurality of combinations of the control axis for the rotation of the jaws about the rotation center lines set by the operator.

In the stretch forming apparatus 10 having the configuration of the axis shown in FIG. 1, for instance, two combinations of the control axis exist when the jaw J_(L) is rotated about the rotation center line A3 set in the appropriate relative position with respect to the die D as shown in FIG. 5. As the first one thereof, there exists a combination of the die table up-and-down axis J_(D1), the slider axis J_(L3) and the rotation axis J_(L5) as shown in FIG. 5(B).

As the second one thereof, there exists a combination of the die table up-and-down axis J_(D1), the die table tilt axis J_(D2), and the slider axis J_(L3) as shown in FIG. 6(B). In the combination shown in FIG. 6(B), for the rotation of the jaw J_(L) by the quantity of rotation Δθ2 about the rotation center line A3, the die D is moved up by a quantity of movement ΔZ2 by the die table up-and-down axis J_(D1), is rotated by a quantity of rotation Δγ by the die table tilt axis J_(D2), and jaw J_(L) is moved in the Y axis direction by a quantity of movement ΔS3 by the slider axis J.

When there are a plurality of combinations of the control axis by which the rotation of the jaws J_(L), J_(R) about the rotation center lines set by the operator for the jaws J_(L), J_(R) can be attained, the control unit of the stretch forming apparatus 10 may inform the operator of the fact through an output unit such as a display. The operator may be made to select, through an input unit such as a keyboard, which combination of the control axis is to be achieved.

Alternatively, the control unit of the stretch forming apparatus 10 may select an optimal combination of the control axis.

Once the operator sets the rotation center lines for the jaws J_(L), J_(R), for instance, the control unit of the stretch forming apparatus 10 calculates a plurality of combinations of the control axis that are required for the rotation of the jaws J_(L), J_(R) about the rotation center lines. For each of the combinations of the control axis, subsequently, the control unit calculates the quantities of operation that are required for rotating the jaws J_(L), J_(R) by specified angles (e.g., 1°) about the rotation center lines set by the operator, for all the control axis included in the combination. The control unit then selects a combination having the largest number of control axis of which the quantities of operation are smaller than a specified value.

Thus the work W can partially be stretched without great change in the positions and postures of the jaws J_(L), J_(R) and the die D. As a result, the stretch forming of the work W can be resumed without intermission after creases are eliminated by the partial stretch of the work W, for instance.

As a measure on condition that it is impossible to rotate the jaws J_(L), J_(R) about the rotation center lines set by the operator for the jaws J_(L), J_(R) (i.e., on condition that there exists no relevant combination of the control axis), in conjunction with that, the control unit of the stretch forming apparatus 10 is preferably configured so as to inform the operator of such a fact and so as to urge the operator to set other rotation center lines.

In the embodiment described above, both of the pair of jaws J_(L), J_(R) are rotated so as to partially stretch the work W. The work W, however, can partially be stretched by either one of the jaws.

In the stretch forming apparatus 10 of the embodiment described above, additionally, the rotation center lines for the jaws J_(L), J_(R) for the partial stretch of the work W are defined by the positions and postures in the die table coordinate system ΣD. That is because there are no control axis for translation of the jaws J_(L), J_(R) only in the vertical direction (the Z axis direction in the system coordinate system ΣS) and because there instead exists the die table up-and-down axis J_(D1) for the up-and-down movement of the die D in the vertical direction. In another stretch forming apparatus having the control axis for the translation of the jaws in the vertical direction, accordingly, the rotation center lines for the jaws may be defined in a coordinate system other than a coordinate system predefined for the die, e.g., in a system coordinate system such as the system coordinate system ΣS of the stretch forming apparatus 10.

In addition, the rotation center line setting unit of the stretch forming apparatus 10 may be configured so as to preset a plurality of rotation center lines for the jaws that are for the partial stretch of the work and so as to make the operator select desired rotation center lines from the plurality of preset rotation center lines. For instance, the rotation center line setting unit is configured so as to preset the rotation center lines A1 through A4 as shown in FIG. 3 and so as to make the operator select any of the rotation center lines A1 through A4. Thus the manual operation for partially stretching the work is further simplified.

Finally, simple examples as shown in FIGS. 4 through 6 are adduced herein for facilitation of understanding as to the invention. The invention, however, is not limited those examples. In a broad sense, the invention is for calculating quantities of operation of the plurality of the control axis that cause the jaws to rotate by any quantity the operator desires about the rotation center lines set arbitrarily by the operator, by solving an inverse kinematics problem, and for synchronously controlling the plurality of control axis on basis of the calculated quantities of operation. Thus any part of the work the operator desires can solely be stretched or can more greatly be stretched than other parts thereof.

The invention can be applied to any stretch forming apparatus as long as the apparatus has a pair of jaws for grasping both ends of a work, a die that is placed between the pair of jaws so as to be in contact with the work, and a plurality of control axis for change in positions and postures of the jaws and the die, irrespective of a number of the control axis. 

1. A stretch forming apparatus comprising: a pair of jaws for pinching end edge side parts of a work having a pair of side edges and a pair of end edges; a die placed between the pair of jaws so as to be in contact with the work; a plurality of control axes for change in positions and postures of the jaws and the die; a rotation center line setting unit for making an operator set rotation center lines for the jaws that are for partial stretch of the work by rotation of the jaws, an operation input unit for rotating the jaws by manual operation about the rotation center lines set by the operator through the rotation center line setting unit, and a control unit for synchronously controlling the plurality of control axes so that the jaws rotate, in accordance with the manual operation by the operator on the operation input unit, about the rotation center lines set by the operator through the rotation center line setting unit.
 2. The stretch forming apparatus according to claim 1, wherein the rotation center line setting unit is configured so as to set the rotation center lines by positions and postures in jaw coordinate systems predefined for the jaws, and wherein the control unit defines the rotation center lines for the jaws that have been defined by the positions and postures in the jaw coordinate systems, by positions and postures in a die coordinate system predefined for the die and controls the control axis for the die and the control axis for the jaws so that the jaws rotate about the rotation center lines defined by the positions and postures in the die coordinate system.
 3. The stretch forming apparatus according to claim 1, wherein the rotation center line setting unit sets the rotation center lines so that the rotation center fines pass through crossing points of a side edge of the work and boundaries between parts of the work pinched by the jaws and the remaining parts thereof.
 4. The stretch forming apparatus according to claim 3, wherein the rotation center line setting unit sets the rotation center lines that extend in a direction orthogonal to surfaces of the parts of the work pinched by the jaws.
 5. The stretch forming apparatus according to claim 3, wherein the rotation center line setting unit sets the rotation center lines along an extending direction of side edges in the parts of the work pinched by the jaws.
 6. The stretch forming apparatus according to claims 1, wherein, on condition that there are a plurality of combinations of the control axes that allow the jaws to be rotated about the rotation center lines set by the operator, the control unit selects a combination including the largest number of the control axis of which quantities of operation for rotation of the jaws are smaller than a specified value, and rotates the jaws by controlling the control axes included in the selected combination. 